Means for transforming mechanical vibrations into electrical vibrations.



L. DE FOREST.

MEANS FOR TRANSFORMING MECHANICAL VlBRATlONS mo ELECTRICAL VIBRATIONS.

APPLICATION FILED 1AN.22.1916- 4 Patented July 15, 1919.

UNITED STATES PATENT OFFICE.

mm DI FOREST, 01' NEW YORK, N. Y., ASSIGNOB TO DIE FOREST RADIO TELEPHQNE AND v COIPANY, NEW YORK, N. Y., A CORPORATION 01' DELAWARE.

mm FOB 'I'RARSI'OBIUG uncnzmcn. mmrrons nrro v VIBBATIONS.

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To all whom it may concern:

Be it known that I, Lna on Forum, a citizen of the United States, residing at New- York, county of Bronx, and State of New York, have made a certain new and useful Inventionin Means for Transformin Mechanical Vibrations into Electrical ibrations, of which the following is a specificat-ion.

'The invention relates to means for changin mechanical into electrical vibrations.

he ob'ect of the invention is to provide means which are simple and efii'cient for changing mechanical vibrations into electrical vibrations, and by mechanical vibrations I mean vibrations created mechanically as distinguished from vibrations created electrically or electro-ma etically,

A further object o the invention is to accomplish the purposes above referred to by means of an evacuated vessel containing electrodes therein.

Further objects of the invention will 'appear more fully hereinafter.

The invention consists substantially in the construction, combination, location and relative arrangement of parts and circuit arrangements associated therewith, all as will be more fully hereinafter set forth, as shown by the accompanying drawing, and finally pointed out in the appended claims.

Referring to the drawing,

Figure 1 shows one circuit arrangement embodying my invention.

Fig. 2 shows a modified construction of the vessel employed in accordance with my invention. I

Fig. 3 is a diagrammatic view showing a modified circuit arrangement.

Fig. 4 shows a further modified arrangement.

The same reference character refers to the same part wherever it occurs throughout the several views.

In the drawings U generally designates an evacuated *vessel, preferably spherical .in form as shown, containing a filament F heated from suitable source, such as a battery A,

controlled by resistance R.

In the arrangement shown in Fig. 1, I prefer to form the filament electrode F, coiled, as shown, and placed in a plane parallel to the plane of the plate electrode, which in this instance is in the form of a circular plate and lpeoueetton of Letter! latent.

- Patented Jul '15 9. Application Med January 22, 1918. Serial Io. 78,678.

is mounted on a wire or conducting rod K sealed in one side of the vessel and extending and rigidly fastened to diaphragm D closmg a mouth piece designated at M. A flux source, suc as battery B, is connected by its negative terminal to one side of the .filament F and by its positive terminalthrough one coil P of a telephone transformer to the plate electrode W, as shown.

The secondary coil S of the telephone transformer 15 connected to the outgoin line and thence to a distant telephone recelver, diagrammatically designated at T.

The operatlon of the device thus described,-

then transmitted over the telephone line L to the telephone receiver T, as will be readily.

understood.

I find that this arrangement which is in substance a substitute for a microphone, is free from most of the imperfections of any -mechanical resistance varying device such as are inherent to the carbon granule micro phone, and that in consequence a clearness and fidelity of sound reproduction is obtained in the telephone receiver far superior to that possible when a microphone is employed.

The magnitude of vibrations obtained in the device shown in Fig. 1, even when the vessel U is made of large diameter, and of thin glass, is not great, and there is obviously a mechanical limit to the nearness with which the plate W, can be placed to the filament or cathode F, in order to insure against actual contact of the two electrodes.

To remedy this one objection I have found that the arrangement shown in Fig. 2, is highly effective. In this form the evacuated vessel U has a long tubular neck G through electrode IV in close proximity to the filament F as hereinbefore described.

The long glass stem or neck C, 1s quite flexible and permits therefore, relatively large movements of the arm or rod K sealed therein. If desired, a metal support E mtg be fastened around the base of the neck as shown, provided with a thumb screw G for slightly bending the glass neck, thereby affording means for adjusting the position of the plate electrode W, relative to the filament F A piece of rubber, felt or other soft material designated at H, forming a tip for the screw G permits the glass neck to be vibrated slightly as impelled by the rod K, and at the same time it dampens any natural vibration of the neck C. It will be noticed that the circuit arrangement of this re is identical to that of Fig. 1, and the principle of operation thereof is the same.

In Fig. 3, I show avessel U similar to that of Fig. 2, but I employ in connection therewith two cold electrodes associated with the filament electrode F. In this arrangement the arm K terminates in a wire interposed between the filament'electrode F and the third electrode Y. The electrode Y is preferably in the form of a plate, bent at an angle as shown, and is supported by a suitable rod J sealed into the vessel U and the plate is connected through a telephone transformer as shown in Figs. 1 and 2, to the telephone T or direct thereto, and to the source B, and one terminal of the filament F all as shown. In this instance an electric charge, the amount and polarity of which is controlled by the potentiometer P', and battery B, connected to the filament F, and the arm K, is maintained on the vibrating member N. The operation of the device described is similar to the operation of the arrangements shown in Figs. 1 and 2.

In. Fig. 4, I show an audion microphone similar to that shown in Figs. 1 and 4. The grid electrode N and the plate electrode W, are connected to the filament F, through inductively associated coils S and'P, respectively of a re enerative oscillating circuit. A tuning con enser G is shown connected around the coil P, and a stopping condenser damped electrical oscillations suitable, for

example, in a radio telephone transmitting system. The amplitudes of these oscillations are modulated by the movements of the voice controlled electrode W.

It is obvious that many other arrangements will readily occur to those skilled in the art without departing from the broad scope of my invention as defined in the claims.

Therefore, what I claim as new and useful and desire to secure b Letters Patent, is:

'1. In a device of the class described, the combination with a source of mechanical vibrations, a vessel provided with a comparatively thin neck, electrodes sealed in said vessel, one of said electrodes extending through said neck and connected to said source, said mechanical ,vibrations. causin corresponding'vibrations of said neck'and variations in an output circuit also connected to said electrodes.

- 2. In a device of the class described, the combination with a source of mechanical vibrations, a vessel provided with a comparatively thin neck, electrodes sealed in said vessel, one of said electrodes extendin through said neck and connected to said source, said mechanical vibrations causin corresponding vibrations of said neck and variations in an output circuit. also connected to said electrodes, and means for detecting the variations of said output circuit. 7

In testimony whereof I have hereunto set.

my hand on this 11th day of J anuary, A. D. 1916.

LEE DE FOREST. 

